Mammalian ovarian folliculogenesis is a precise series of developmental events that requires the cooperative efforts of several cell types and the integration of a complex set of chemical messages that ultimately lead to successful maturation and ovulation of the oocyte. Within the past few decades it has become clear that many of the steps in the metabolic pathways within the ovary are under the combined control of extraovarian (hypophyseal) and introvarian factors. The overall objective of this proposal is to examine fundamental aspects of the hormonal mechanisms responsible for folliculogenesis. This proposal is concerned with the mechanism of action of follicle stimulating hormone (FSH) and its role in early folliculogenesis. Specifically the cellular mechanism underlying FSH induced alteration of ovarian granulosa cell function will be addressed. The functional role of FSH binding, internalization and subsequent intracellular processing in the initiation of steroid secretion and LH receptor induction will be evaluated. Experiments outlined in this proposal will: 1) analyze the binding of internalization and cellular processing of fluorescent derivatives of FSH in living granulosa cells using time lapse video image intensification microscopy; 2) determine at the ultrastructural level the distribution and fate of the FSH receptor following hormone binding; and 3) examine the effect of FSH receptor occupancy on the dynamics of the LH/hCG receptor.